The optimal condition of double-paper synergy test in the detection of bacteria producing extended-spectrum β-lactamase (ESBLS) was studied. In 244 isolates of Enteric bacilli，Klebsiella pneumonia，Enteric cloacae，there were 49 ESBLS-producing strains with the positive rate being 19.67 %. Five ESBLS-producing strains were detected in Pseudomonas maltophilla. One ESBLS-producing strains was detected in Pseudomonas aeruginose，Enteric aerogenes and Citrobacter，respectively. The optimal substrates of double-paper synergy test were cefotaxime，aztreonam and cefepime，and the interspace was 25 mm. This method was still a simple，economical and appropriate method in the detection of ESBLS-producing isolates.